In general, the black middle class that arose in the South after Reconstruction came from a small class of entrepreneurs who provided services (and some goods) to fellow African Americans. African American businesses were not going to be able to attract white patrons and so black businessmen had to cater to other blacks.
Much of the middle class worked as semi-professionals. There were ministers of black churches and there were black undertakers. There were also operators of small grocery stores, barber shops, etc.
In other words, the black middle class did not spring up by working as management or white-collar types in big businesses. Instead, they tended to be small entrepreneurs catering to an African American clientele.